Abstract
Objectives
The objective of this study was to determine which patient traits, behaviors, external tooth and/or crack characteristics correlate with the types of symptoms that teeth with visible cracks exhibit, namely pain on biting, pain due to cold stimuli, or spontaneous pain.
Methods
Dentists in the National Dental Practice-Based Research Network enrolled a convenience sample of subjects each of whom had a single, vital posterior tooth with at least one observable external crack (cracked teeth); 2858 cracked teeth from 209 practitioners were enrolled. Data were collected at the patient-, tooth-, and crack-level. Generalized estimating equations were used to obtain significant (p < .05) independent odds ratios (OR) associated with teeth that were painful for 10 outcomes based on types of pain and combinations thereof.
Results
Overall, 45% of cracked teeth had one or more symptoms. Pain to cold was the most common symptom, which occurred in 37% of cracked teeth. Pain on biting (16%) and spontaneous pain (11%) were less common. Sixty-five percent of symptomatic cracked teeth had only one type of symptom, of these 78% were painful only to cold. No patient-, tooth- or crack-level characteristic was significantly associated with pain to cold alone. Positive associations for various combinations of pain symptoms were present with cracks that: (1) were on molars; (2) were in occlusion; (3) had a wear facet through enamel; (4) had caries; (5) were evident on a radiograph; (6) ran in more than one direction; (7) blocked transilluminated light; (8) connected with another crack; (9) extended onto the root; (10) extended in more than one direction; or (11) were on the distal surface. Persons who were <65 yo or who clench, grind, or press their teeth together also were more likely to have pain symptoms. Pain was less likely in teeth with stained cracks or exposed roots, or in non-Hispanic whites.
Conclusions
Although pain to cold was the most commonly noted pain associated with symptomatic cracked teeth, no patient-, tooth- or crack-level characteristic was significantly associated with pain to cold alone. Characteristics were only associated with pain on biting and/or spontaneous pain with or without pain to cold.
Clinical significance
Although often considered the most reliable diagnosis for a cracked tooth, pain on biting is not the most common symptom of a tooth with a visible crack, but rather pain to cold.
1
Introduction
Cracks in teeth, particularly posterior teeth, are a common finding. A comprehensive review on cracked teeth reported incidence rates varying between 0%−70%, depending on the tooth type and location [ ]. A recent practice-based study found that 70% of patients had at least one posterior tooth with visible fracture lines, 21% of which were symptomatic. [ ]. A variety of symptoms have been attributed to cracked teeth, some of which are quite rare, such as trigeminal autonomic cephalalgia [ , ], The most commonly reported symptoms of cracked teeth are pain to cold and pain on biting [ ]. A study of 154 symptomatic cracked teeth reported that 96% were painful on biting and 45% were sensitive to cold [ ]. No clinical study to date has reported on commonalities of various factors to symptomology. Therefore, the purpose of this observational practice-based study was to correlate various patient-, tooth- and crack-level characteristics with the type of symptoms (spontaneous pain, pain on biting, pain to cold) exhibited by symptomatic cracked teeth in patients from selected practices participating in the National Dental Practice-based Research Network (National Dental Network).
2
Methods
A detailed description of the enrollment and data collection processes is provided in a previous publication [ ]. Briefly, a convenience sample of subjects between 19 and 85 years old having a single, vital posterior tooth with at least one observable external crack (referred to in this paper as cracked teeth) was enrolled by dentists in the National Dental Practice-based Research Network [ ]. Dentists were asked to enroll 20 eligible subjects, or as many as they could in eight weeks, whichever came first. The Institutional Review Board (IRB) of the lead investigators (TH & JF) reviewed and approved the study, as did the IRBs for the network’s six regions. All subjects were consented for entrance into the study.
Dentist and practice personnel were trained in data collection; data were collected at the patient-, tooth-, and crack level. Data forms are publicly available at [http://nationaldentalpbrn.org/study-results/cracked-tooth-registry.php]. Tooth vitality was confirmed, preferably with cold [ ] (e.g., refrigerant, ice) although some dentists used other methods such as air, air/water spray, or electric pulp testing. Spontaneous pain information was obtained via patient report, with pain to cold determined using the aforementioned refrigerant, ice, or air/water spray, and pain on biting confirmed by having the patient occlude on a device or instrument placed on the occlusal surface of the cracked tooth. To help patients distinguish pain, i.e., a heightened response to the cold or bite assessment, from an ordinary response, dentists were asked to also perform these tests on a “normal” (e.g., contralateral) tooth.
Enrollment proceeded in two phases: a pilot phase from April-July 2014, in which 183 patients were enrolled by 12 practices, and a main launch phase that occurred from October 2014-April 2015. In a previous report [ ] we described 2975 patients/cracked teeth enrolled by 209 practitioners. This current report excludes 96 cracked teeth that were partially or completely fractured (violation of eligibility criteria), and 21 patients we identified as duplicates, leaving 2858 patients/cracks.
Symptomatic classification: Teeth were classified as symptomatic if they were sensitive to cold or had pain on biting or were spontaneously painful. Types of symptoms could be “present”, i.e., present alone or in any combination of two or three symptoms; “sole”, i.e., one symptom alone; or in “combination”, i.e., any two or three symptoms occurring together.
Analysis: Overall frequencies were obtained among asymptomatic cracked teeth (no pain to cold, pain on biting, or spontaneous pain), and symptomatic cracked teeth, separately by type of symptom (pain to cold, pain on biting or spontaneous pain), and by patient-, tooth- and crack-level characteristics. Initial analyses with patient demographics and behaviors were used to inform categorization for the regression model. Associations between characteristics present in less than one percent of the patient population and type of symptoms were not examined because of difficulty modeling and imprecise estimates. In a univariable fashion, each patient-, tooth-, and crack-level characteristic was entered into a logistic regression model that used generalized estimating equations (GEE) method that adjusted for clustering of patients within the practice, implemented using PROC GENMOD in SAS with CORR = EXCH option. All characteristics with p < .05 after adjusting only for clustering of patients within the practice were entered into a full model. This was followed with backwards elimination, again using GEE to adjust for clustering to identify independent associations with symptomology, being retained if p < .05, in a reduced model. The models were further refined by requiring a magnitude of association to be either greater than an odds ratio (OR) of 1.5 or less than 0.6. After fitting the final model, all interaction terms were tested for significance at the 0.05 level. All analyses were performed separately by type of symptoms. The referent group for all comparisons was the asymptomatic group.
Additional analyses were performed examining associations with patients having only one type of symptom, then for each combination of two types of symptoms, and lastly for those with all three types of symptoms. This was done to better ascertain if identified characteristics were associated with solely or primarily one type of symptom, if the magnitude of association differed for the type of symptoms, and if the magnitude of associations increased or changed with combinations of symptoms. Because power was limited for one symptom type alone and specified combination analyses, the significance level for entry into the full model and then retention in the reduced model was relaxed (increased) to 10%. Associations among patient-, tooth- and crack-level characteristics were examined, using GEE, to help explain/understand variations in associations across models (Supplemental Tables 1–3). All odds ratios (ORs) and p-values reported below were adjusted for clustering of patients within practitioner with GEE. All analyses were performed using SAS software (SAS v9.4, SAS Institute Inc., Cary NC).
2
Methods
A detailed description of the enrollment and data collection processes is provided in a previous publication [ ]. Briefly, a convenience sample of subjects between 19 and 85 years old having a single, vital posterior tooth with at least one observable external crack (referred to in this paper as cracked teeth) was enrolled by dentists in the National Dental Practice-based Research Network [ ]. Dentists were asked to enroll 20 eligible subjects, or as many as they could in eight weeks, whichever came first. The Institutional Review Board (IRB) of the lead investigators (TH & JF) reviewed and approved the study, as did the IRBs for the network’s six regions. All subjects were consented for entrance into the study.
Dentist and practice personnel were trained in data collection; data were collected at the patient-, tooth-, and crack level. Data forms are publicly available at [http://nationaldentalpbrn.org/study-results/cracked-tooth-registry.php]. Tooth vitality was confirmed, preferably with cold [ ] (e.g., refrigerant, ice) although some dentists used other methods such as air, air/water spray, or electric pulp testing. Spontaneous pain information was obtained via patient report, with pain to cold determined using the aforementioned refrigerant, ice, or air/water spray, and pain on biting confirmed by having the patient occlude on a device or instrument placed on the occlusal surface of the cracked tooth. To help patients distinguish pain, i.e., a heightened response to the cold or bite assessment, from an ordinary response, dentists were asked to also perform these tests on a “normal” (e.g., contralateral) tooth.
Enrollment proceeded in two phases: a pilot phase from April-July 2014, in which 183 patients were enrolled by 12 practices, and a main launch phase that occurred from October 2014-April 2015. In a previous report [ ] we described 2975 patients/cracked teeth enrolled by 209 practitioners. This current report excludes 96 cracked teeth that were partially or completely fractured (violation of eligibility criteria), and 21 patients we identified as duplicates, leaving 2858 patients/cracks.
Symptomatic classification: Teeth were classified as symptomatic if they were sensitive to cold or had pain on biting or were spontaneously painful. Types of symptoms could be “present”, i.e., present alone or in any combination of two or three symptoms; “sole”, i.e., one symptom alone; or in “combination”, i.e., any two or three symptoms occurring together.
Analysis: Overall frequencies were obtained among asymptomatic cracked teeth (no pain to cold, pain on biting, or spontaneous pain), and symptomatic cracked teeth, separately by type of symptom (pain to cold, pain on biting or spontaneous pain), and by patient-, tooth- and crack-level characteristics. Initial analyses with patient demographics and behaviors were used to inform categorization for the regression model. Associations between characteristics present in less than one percent of the patient population and type of symptoms were not examined because of difficulty modeling and imprecise estimates. In a univariable fashion, each patient-, tooth-, and crack-level characteristic was entered into a logistic regression model that used generalized estimating equations (GEE) method that adjusted for clustering of patients within the practice, implemented using PROC GENMOD in SAS with CORR = EXCH option. All characteristics with p < .05 after adjusting only for clustering of patients within the practice were entered into a full model. This was followed with backwards elimination, again using GEE to adjust for clustering to identify independent associations with symptomology, being retained if p < .05, in a reduced model. The models were further refined by requiring a magnitude of association to be either greater than an odds ratio (OR) of 1.5 or less than 0.6. After fitting the final model, all interaction terms were tested for significance at the 0.05 level. All analyses were performed separately by type of symptoms. The referent group for all comparisons was the asymptomatic group.
Additional analyses were performed examining associations with patients having only one type of symptom, then for each combination of two types of symptoms, and lastly for those with all three types of symptoms. This was done to better ascertain if identified characteristics were associated with solely or primarily one type of symptom, if the magnitude of association differed for the type of symptoms, and if the magnitude of associations increased or changed with combinations of symptoms. Because power was limited for one symptom type alone and specified combination analyses, the significance level for entry into the full model and then retention in the reduced model was relaxed (increased) to 10%. Associations among patient-, tooth- and crack-level characteristics were examined, using GEE, to help explain/understand variations in associations across models (Supplemental Tables 1–3). All odds ratios (ORs) and p-values reported below were adjusted for clustering of patients within practitioner with GEE. All analyses were performed using SAS software (SAS v9.4, SAS Institute Inc., Cary NC).
3
Results
In all, 2858 patients/cracks were enrolled by 209 practitioners, with a mean/median of 14.8/15 patients per practice and a range of 1 to 20; 1561 (54%) of the teeth were asymptomatic. Figs. 1–3 show the distribution of symptom types. Pain was reported from several stimuli, referred to here as “types of pain.” Among the 1297 symptomatic patients/teeth, pain to cold was present in 1055 (81%), pain on biting was present in 459 (35%), and 367 (28%) exhibited spontaneous pain; 409 (35%) had more than one type of symptom.
3.1
Patient-level characteristics
The mean age (SD) of the patients was 54 (12);, the median age (inter-quartile range) was 55 (46–62) years, with a range from 19 to 85 years. Overall, 1813 (63%) patients were female, 2394 (85%) were non-Hispanic white, 2213 (77%) had some dental insurance, and 2432 (86%) had some college education. Two-thirds of the patients (N = 1900, 66%) reported clenching, grinding, or pressing their teeth together, and 2190 of 2690 main launch subjects (81%) reported feeling at least some stress when queried, with over one-third reporting feeling stress at least weekly (N = 1048, 39%). (Data on stress were not obtained in the pilot phase.)
3.2
Tooth-level characteristics
Overall, the majority of cracked teeth were molars (N = 2332; 82%), with more than half in the mandibular arch (N = 1675, 59%). Most of the external cracks, 92%, were on a tooth with a restoration: 71% of cracked teeth had one restoration, 19% had two restorations and 2% had 3–4 restorations. Virtually all study teeth had an opposing tooth (N = 2793, 98%); most were opposed by a natural or restored tooth (N = 2612, 91%). Twenty-two percent (N = 638) had root exposure, and 24% (N = 676) presented with at least one wear facet through enamel. A lesser percentage of subject teeth had caries present (N = 302, 11%) or a non-carious cervical lesion (NCCL) (N = 254, 9%). Only 53 (2%) had evidence of a crack on a radiograph. Removable partial denture abutment teeth (N = 20, 0.7%) and fixed partial denture abutment teeth (N = 3, 0.1%) were too rare to assess by type of symptom.
3.3
Crack-level characteristics
The majority of cracked teeth had a crack that was stained (N = 2319; 81%), connected with a restoration (N = 2095; 73%), was detectable with an explorer (N = 1980; 69%), blocked trans-illuminated light (N = 1862; 65%) and/or ran in a vertical direction (N = 2674; 94%). Tooth surfaces with cracks were distributed in a narrow range, from 44% (N = 1267) that involved the occlusal surface to 51% (N = 1463) involving the lingual surface; 1028 (36%) had a crack that involved two or more surfaces.
3.4
Types of symptoms
Cracked teeth with one type of symptom (N = 850, 66% of symptomatic) ( Table 1 ):
- •
666 ONLY sensitive to cold (63% of all those sensitive to cold; 78% of those with one type of pain)
- •
120 ONLY pain on biting (26% of all those with pain on biting; 14% of those with one type of pain)
- •
64 ONLY had spontaneous pain (17% of all those with spontaneous pain; 8% of those with one type of pain)
| Overall categories of symptom type (not mutually exclusive) | Each type alone | Combinations of 2 types of symptoms | All 3 symptoms | |||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Cold | Biting | Spontaneous | Cold | Biting | Spontaneous | Cold and bite | Cold and spontaneous | Bite and spontaneous | Cold, Bite, & Spontaneous | |
| (N = 1055) | (N = 459) | (N = 367) | (N = 666) | (N = 120) | (N = 64) | (N = 144) | (N = 180) | (N = 58) | (N = 137) | |
| OR | OR | OR | OR | OR | OR | OR | OR | OR | OR | |
| Characteristic a | (95% CI) | (95% CI) | (95% CI) | (95% CI) | (95% CI) | (95% CI) | (95% CI) | (95% CI) | (95% CI) | (95% CI) |
| Patient level | ||||||||||
| Non-Hispanic White race | w | x | w | w | 0.52 * (0.33–0.82) | 0.58 * (0.38–0.89) | ||||
| Age less than 65 years | w | 1.72 *** (1.29–2.28) | x | w | 2.25 ** (1.13–4.49) | w | 2.33 ** (1.26–4.31) | |||
| Clench, grind, OR press teeth together | w | 1.53 *** (1.25–1.89) | w | 1.61 * (1.07–2.43) | 1.68 † (0.96–2.97) | 1.62 *** (1.26–2.07) | x | x | x | |
| Tooth level | ||||||||||
| Molar | 1.60 *** (1.23 − 1.93) | 2.41 *** (1.74–3.32) | 2.32 *** (1.68–3.21) | x | 2.81 *** (1.32–5.99) | 2.20 *** (1.49–3.25) | 1.93 ** (1.16–3.20) | 3.63 *** (1.55–8.53) | 2.50 *** (1.44–4.36) | |
| In occlusion w/opposing tooth | 2.50† (0.83–7.57) | |||||||||
| Wear facet through enamel | x | w | x | 1.60 † (1.02–2.53) | x | |||||
| Exposed roots | x | w | 0.35 ** (0.15–0.82) | 0.62 * (0.40–0.95) | ||||||
| Caries present | w | x | 1.79 ** (1.30–2.46) | 2.87 ** (1.90–4.32) | ||||||
| NCCL present | 0.55 ** (0.34–0.88) | 0.33 * (0.10–1.05) | x | |||||||
| Evidence of crack(s) on radiograph | 2.53 * (1.24–5.17) | 2.70 ** (1.44–5.05) | 2.79 † (1.14–6.81) | 4.88 * (2.31–10.31) | ||||||
| Crack level | ||||||||||
| Stained | 0.50 *** (0.37–0.69) | 0.56 ** (0.42–0.76) | 0.31 ** (0.17–0.55) | 0.60 * (0.42–0.87) | 0.33 ** (0.18–0.60) | 0.49 * (0.30–0.79) | ||||
| Blocks transilluminated light | w | 1.59 *** (1.21–2.08) | w | w | 2.34 * (1.19–4.61) | 2.09 *** (1.40–3.12) | ||||
| Connects with another crack | 1.75 * (1.11–2.77) | |||||||||
| Extends to root | w | 2.02 * (1.25–3.25) | ||||||||
| More than 1 direction | 1.59 ** (1.15–2.19) | x | ||||||||
| Distal surface | w | 1.59 *** (1.28–1.98) | w | x | 1.60 * (1.05–2.43) | 1.86 * (1.19–2.92) | w | 1.85 * (1.18–2.90) | 1.61 * (1.10–2.34) | |
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